Carburetor



970 5. OTTERBACH ET AL 3,511,220

CARBURETOR Filed Sept. 4, 1968 19 GEA/T5 United States Patent 3,511,220CARBURETOR Gerd Otterbach, Hansen, and Giinter Troch, Schweinfurrt,

Germany, assignors to Fichtel & Sachs AG, Schwemfurt, Germany FiledSept. 4, 1968, Ser. No. 757,383 Claims priority, application Germany,Sept. 9, 1967, 1,576,551 Int. Cl. F02b 77/00; F02m 37/02; F02p 9/00 US.Cl. 123-198 12 Claims ABSTRACT OF THE DISCLOSURE A carburetor for agasoline engine in which a single control knob, when turned in onedirection, sequentially causes tickling of the float, opening of thechoke, closing of the throttle to idling speed, grounding of theignition, and shut-off of the fuel supply conduit. The knob is mountedon a shaft carrying the choke plate, the grounding switch, and theshut-off valve. Abutments on the choke plate operate the throttle andthe tickler rod.

BACKGROUND OF THE INVENTION This invention relates to carburetors forinternal combustion engines and particularly to a manual operatingsystem for operating the choke, throttle, and other movable elements ofa carburetor during starting and shutdown of the associated engine.

The invention will be described hereinafter with specific reference to aone-cylinder gasoline engine for a power tool or similar applications,but a carburetor operating system of the invention may be employed withcarburetors of other internal combustion engines, as will be apparent tothose skilled in the art.

It is known to interconnect operating elements in a carburetor of thetype described so that one control member may sequentially operate morethan one movable carburetor element. The object of the invention is theprovision of a manually controlled carburetor which can be set for itsseveral modes of operation during engine starting and shut-down by meansof a single control member.

SUMMARY OF THE INVENTION According to the invention, a single controlmember mounted on a support for movement relative to the same isconnected with the choke, the throttle, an ignition shorting switch, andthe fuel shut-off valve of the carburetor in such a manner that theseveral carburetor elements and the switch are sequentially operated inresponse to movement of the control member. The carburetor shell whichdefines the air intake conduit of the carburetor preferably carries theshut-off valve and serves as a support for the shaft of the controlmember.

As the control member sequentially passes through several positionsduring its movement in one direction, the choke is first moved away fromits operative or starting position in which it largely obstructs the airintake conduit. In a subsequent position of the control member, thethrottle is moved into the operative or idling position in which itlargely obstructs the air intake conduit. When the control member movesfurther, the ignition is shorted and the fuel supply is shut off.

The choke may be mounted on the same shaft as the control member forangular displacement about the shaft axis which may be parallel to theaxis of the air intake conduit.

Other features, additional objects and many of the attendant advantagesof the invention will readily become apparent from the followingdetailed description of a 3,511,220 Patented May 12, 1970 preferredembodiment when considered in connection with the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 shows a carburetor of the invention in front elevation withoutits outer casing and control knob;

FIG. 2 shows the carburetor of FIG. 1 in side elevation in the directionof the arrow A;

FIG. 3 illustrates the same carburetor in rear elevation;

FIG. 4 is a fragmentary sectional view of the device in section on theline IVIV;

FIG. 5 is a sectional view taken on the line V-V in FIG. 1; and

FIG. 6 shows the outer carburetor casing and the carburetor control knobin a view corresponding to that of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing indetail, and initially to FIGS. 1 to 4, there is seen 'as much of anotherwise conventional carburetor as is needed for an understanding ofthis invention. A portion of the carburetor shell 10 encloses an airintake duct 12, and another portion forms a float chamber 14 in which afloat 16 is pivotally mounted on a pin 18. The float chamber 14 receivesfuel from a nonillustrated tank through a fuel supply conduit 20equipped with a shut-off valve 22 and a float-operated needle valve 24.Y

A fuel line 26 communicates with the chamber 14 and terminates in anorifice in the air intake conduit 12. A choke 28 largely obstructs theduct 12 in the view of FIG. 1 ahead of the fuel line orifice, and athrottle 30 similarly obstructs the duct '12 in the view of FIG. 3downstream from the fuel line orifice. The shell 12 is provided withapertures 32 for fasteners which normally attach the shell 10 to theinlet of the associated, non-illustrated engine cylinder.

The choke 28 mainly consists of a plate 34 mounted on a shaft 36 whichis journaled in the shell 10. The axis of the shaft 36 is spacedlyparallel to the longitudinal axis of the duct 12. The throttle 30 ismounted on a pin 38 which is also journaled in the shell 10 and isbiased by a torsion spring 40 toward the angular position of thethrottle 30 illustrated in FIG. 3. A sheet metal arm 42 radiallyprojects from the shaft 38 outside the duct 12 and has a forked free end44, the only illustrated element of a throttle linkage connecting theshaft 38 to an automatic speed governor (not shown) as is conventionalin some power tool applications and not directly relevant to thisinvention.

A bore in the portion of the shell 10 enclosing the float chamber 14slidably receives a tickler rod 46 whose inner end is directed fromabove toward the float 16 in the chamber 14, and which is biased outwardof the chamber by a helical compression spring 48. Outward movement ofthe tickler rod 46 beyond the position illustrated in FIG. 1 isprevented by non-illustrated stops.

The apparatus described so far functions in a conventional manner. Whenthe valve 22 is open, fuel flows through the conduit 20 into the chamber14 until the rising float 16 closes the needle valve 24. Fuel is drawnfrom the chamber 14 into the duct 12 by the vacuum of the connectedengine and is atomized in the duct. During engine start-up, the plate 34of the choke 28 largely obstructs the flow of air into the throat of theduct 12 so that a fuel mixture rich in gasoline is fed to the enginethrough the opened throttle 30. In order further to enrich the initialfuel mixture, the tickler rod 46 may be depressed prior to starting tofill the chamber 14 beyond the level automatically maintained by thefloat 16 during normal operation, the float being held away from theneedle valve 24 by the rod 46.

After the engine has started and warmed up sufiiciently, the choke 28 isopened and the throttle 30 is operated normally by the throttle linkage.It is biased toward the idling position seen in FIG. 3 by the spring 40.Ultimately, the engine is stopped by shutting the valve 22. Thisinvention is concerned mainly with a control mechanism which operatesthe afore-described and other elements of the carburetor and associatedother engine elements in a particularly convenient and simple manner.

The actuating shaft 36 on which the choke plate 34 is mounted carries aU-shaped prong 52 on one of its axial ends outside the shell 10. Theprongs are somewhat resilient and can slida'bly engage conforminggrooves of a control knob 54, as is shown in FIG. 4 only. The knobcoaxially turns with the shaft 36 and with the choke plate 34 mounted onthe shaft. An abutment 56 projects from the plate 34 in such a mannerthat it can engage and depress the tickler rod 46 "when the shaft 36 isturned counter-clockwise from the position seen in FIG. 1.

As is best seen in FIG. 5, the plate 34 of the choke 28 has an edge 58which abuts against a leaf spring 60' in the position shown in fulllines in FIG. 5. The spring 60 is attached to the shell 10 at 62. Whenthe choke 28 is moved toward the position shown in broken lines in FIG.by turning the knob 54 and the shaft clockwise, as viewed in FIG. 1, thespring 60 is bent resiliently in the direction of the arrow 64 intoabutting engagement with a wire link 66 attached to the arm 42, therebymoving the link 66 in the direction of the arrow 68, and returning thethrottle 30 to the idling position of FIG. 3 regardless of the conditionof the throttle linkage portion not seen in the drawing.

The fuel shut-off valve 22 includes a stationary valve housing 70fixedly attached to the shell 10, a valve disc 72 mounted on the shaft36, and a gasket 74 interposed between the housing 70 and the disc 72.Two longitudinal portions of the fuel supply conduit 20 have respectiveorifices in the flat wall of the housing 70 opposite the disc 72. Theface of the latter opposite the housing 70 has a groove 76 which has theshape of an open ring of circular curvature about the axis of the shaft36. The gasket 74 is perforated to permit the orifices of the conduit 20in the housing 70 to be connected or separated by turning the disc 72 bymeans of the knob 54 and the shaft 36.

The axial end of the shaft 36 remote from the knob 54 carries themovable contact 78 of an ignition shorting switch 82 whose fixed contact80 is mounted on the shell and grounded to the shell. The movablecontact 78 is electrically insulated from the shaft 36 and connected tothe hot wire of the ignition system in a manner not shown in detail inthe drawing, but known in itself.

The angular distribution of the several elements which transmit movementfrom the shaft 36 and the knob 54 to the operating elements describedabove will be evident from FIG. 6 which shows the outer casing 88 of thepartly illustrated engine and carburetor. The main portion of thecontrol knob 54 is located outside the casing 88, and only the narrowneck of the knob reaches through an opening in the casing for engagementby the prong 52. An arrow 84 molded into the knob cooperates with ascale 86 on the casing 88 to indicate the angular position of the knob54 and of its shaft 36, and the resulting condition of the carburetor.

As seen in FIG. 6, the arrow 84 points at the index mark start of thescale 86 in which the choke 28 is in the position of FIG. 1. Prior tostarting the engine, the knob is briefly turned counterclockwise intothe position tickle to flood the chamber 14 with fuel if so desired. Itis then returned to the start position, the non-illustrated ignitioncircuit is closed, and the engine is started by means of a pull rope ifso equipped. The closed choke 28 causes an enriched fuel mixture to besupplied to the engine.

When the latter has warmed up sufliciently, the knob 54 is turned toposition run, thereby removing the choke plate 34 from the air intakeduct 12, and the engine runs thereafter at the speed set by itsgovernor.

When the engine is to be shut down, the control knob 54 is turnedfurther in a clockwise direction to idle, thereby closing the throttle,as seen in FIG. 5, and slowing the engine. When the knob 54 isultimately turned to position stop, the ignition circuit is grounded bythe switch 82, and the fuel supply conduit 20 is interrupted at thevalve 22. The engine stops.

Prior to the next operating cycle, the knob is returned to the positionstart, thereby opening the switch 82 and the valve 22. All functions ofthe carburetor which require intervention of the operator are thus setby the single knob 54 by an angular movement of the same in onedirection for each operating cycle.

What is claimed is:

1. In a carburetor for an internal combustion engine having an airintake conduit (12), a float chamber (14), a float (16) in said chamber(14), a fuel supply conduit (20) communicating with said chamber (14), afuel line (26) connecting said chamber (14) with a portion of said airintake conduit (12), a float valve (24) in said fuel supply conduit (20)adapted to be operated by said float (16), a choke (28) and a throttle(30') oppositely spaced in said air intake conduit (12) fromsaid portionof the same, a grounding switch (82) for grounding the ignition circuitof said engine, a shut-off valve (22) in said fuel supply conduit (20),and operating means for operating said choke (28), said throttle (30),said switch (82), and said shut-off valve (22), the improvement in theoperating means which comprises:

(a) a support (10);

(b) a single control member (54) mounted on said support (10) formovement relative to the same; and

(c) motion transmitting means (52, 56) connecting said control member(54) with said choke (28), said throttle (30), said switch (78) and saidshut-off valve (22) for sequentially operating the same in response tosaid movement of said control member 54 2. In a carburetor as set forthin claim 1, said shut-off valve (22) being mounted on a shell (10)defining said air intake conduit (12) therein.

3. In a carburetor as set forth in claim 1, said control member (54)during said movement thereof sequentially passing through a plurality ofpositions when moving in one direction; said choke (28) being moved awayfrom an operative position thereof in which the choke largely obstructssaid air intake conduit (12) when said control member (54) moves throughone of said positions thereof, said throttle (30) being moved into anoperative position thereof in which the throttle largely obstructs saidair intake conduit (12) when said control member (54) moves throughanother of said positions thereof, later than said one position duringmovement in said one direction; said switch (82) being closed and saidshut-off valve (22) being closed when said control member (54) movesbeyond said other position.

4. In a carburetor as set foith in claim 3, said support including ashell (1) defining said air intake conduit (12) therein, said motiontransmitting means including a shaft (36) mounted on said shell (10')for angular displacement about the axis thereof, said control member(54) being mounted on said shaft (36) for angular displacementtherewith, said displacement constituting said movement of said controlmember (54).

5. In a carburetor as set forth in claim 4, said choke (28) beingmounted on said shaft (36).

6. In a carburetor as set forth in claim 5, said air intake conduit (12)having an axis parallel to the axis of said shaft (36), said chokeincluding a plate member (34) moving into and out of said air intakeconduit (12) during said angular displacement of said shaft (36).

7. In a carburetor as set forth in claim 4, tickler means (46) mountedon said shell for moving said float (16) in a direction to open saidfloat valve (24), said motion transmitting means including abutmentmeans (56) mounted on said shaft (36) and enga-geable with said ticklermeans (46) for operating the same.

8. In a carburetor as set forth in claim 7, said abutment means (56)engaging said tickler means (46) during said movement of said controlmember (54) in said one direction prior to the control member (54)passing through said one position thereof.

9. In a carburetor as set forth in claim 8, said choke (28) beingmounted on said shaft (36) and carrying said abutment means (56).

10. In a carburetor as set forth in claim 4, said motion transmittingmeans including cooperating abutments (58,

atively connected to said throttle 11. In a carburetor as set forth inclaim 10, one of said abutments (60) being yieldably resilient.

12. In a carburetor as set forth in claim 4, said shut-off valve (22)including a valve chamber and a valve member (72) mounted on said shaft(36) and rotatable relative to said valve chamber (70) between avalveopening and a valve-closing position.

References Cited UNITED STATES PATENTS 1,770,264 7/1930 Eslinger123146.5 3,338,565 8/1967 Heid 261-70 3,373,725 3/1968 Arpaia l23179 XRFOREIGN PATENTS 956,890 4/1964 Great Britain.

WENDELL E. BURNS, Primary Examiner US. Cl. X.R.

